Memory System and Memory System Control Method

2. The memory system according to claim 1, wherein the memory controller is configured to change a writing mode of one of the plurality of second blocks which has been set in the second mode to the first mode when a second condition different from the first condition is satisfied after the writing mode of the first block has been changed to the second mode.

4. The memory system according to claim 3, wherein the first condition includes a condition based on a lowest valid cluster ratio among the valid cluster ratios of the plurality of second blocks.

5. The memory system according to claim 3, wherein the first condition includes a condition related to a range of the valid cluster ratios of the plurality of second blocks.

6. The memory system according to claim 3, wherein the first condition includes a condition related to the valid cluster ratios of the plurality of second blocks after a predetermined time elapses since writing into the plurality of second blocks.

8. The memory system according to claim 7, wherein the first condition based on the write amount of the garbage collection in the plurality of second blocks is that the write amount of the garbage collection in the plurality of second blocks exceeds a threshold.

11. The memory system according to claim 2, wherein the second condition includes a condition based on a fact that the first condition is no longer satisfied.

12. The memory system according to claim 2, wherein the second condition includes a condition related to an idle state made by a host connected to the memory system.

16. The memory system control method according to claim 15, wherein the first condition includes a condition based on a lowest valid cluster ratio among the valid cluster ratios of the plurality of second blocks.

17. The memory system control method according to claim 16, wherein the first condition includes a condition related to a range of the valid cluster ratios of the plurality of second blocks.

18. The memory system control method according to claim 16, wherein the first condition includes a condition related to the valid cluster ratios of the plurality of second blocks after a predetermined time elapses since writing into the plurality of second blocks.

20. The memory system control method according to claim 19, wherein the first condition based on the write amount of the garbage collection in the plurality of second blocks is that the write amount of the garbage collection in the plurality of second blocks exceeds a threshold.